The present invention relates to a radiography system, or more particularly, to a radiography system that scans a subject with a radiation so as to acquire projection data, and reconstructs images of the subject using the acquired projection data.
Radiography systems including an X-ray computed tomography (CT) system reconstruct images of a subject's section on the basis of projection data acquired from the subject by scanning the subject, who lies down in a radiographic space, with a radiation.
The X-ray CT system is applied to diverse usages including medical use and industrial use, and used for, for example, fluoroscopy that is conducted using a treatment instrument such as a puncture needle. In the fluoroscopy, the X-ray CT system acquires in real time images of a subject's section and displays the images. An operator inserts the puncture needle to an object region of the subject, and checks the position of the puncture needle while looking at the images of the section displayed in real time in the X-ray CT system (refer to, for example, Patent Document 1, Patent Document 2, and Patent Document 3).
[Patent Document 1] Japanese Unexamined Patent Application Publication No. 2001-299742
[Patent Document 2] Japanese Unexamined Patent Application Publication No. 2001-299741
[Patent Document 3] Japanese Unexamined Patent Application Publication No. 2001-276056
To be more specific, in the foregoing fluoroscopy, first, a preliminary scan is performed on a region including an object of examination in a subject prior to a main scan intended to perform treatment using a puncture needle. Planar images that two-dimensionally represent a plurality of subject's axial planes are constructed. In other words, images representing a plurality of different slice planes that are lined longitudinally to the direction of the subject's body axis are constructed two-dimensionally. An operator uses the planar images constructed by performing the preliminary scan to determine the position of an object of examination. Thereafter, the X-ray CT system performs the main scan, and displays in real time the planar images of a section containing a region which covers the object of examination. Herein, the X-ray CT system displays the images of the plurality of different axial planes, that is, slice planes lined longitudinally to the subject's body axis. The operator references the planar images of the axial planes constructed by performing the preliminary scan and the planar images of the plurality of different axial planes displayed in real time during the main scan. Based on the planar images resulting from the preliminary scan, the puncture needle is inserted from a predetermined position. The operator observes the images of the sections displayed in real time and an image representing the needlepoint of the puncture needle. After the operator confirms that the puncture needle has reached the object of examination, the operator treats the subject using the puncture needle so as to achieve fluoroscopic diagnosis.
As mentioned above, in the fluoroscopy, the operator references the planar images of the axial planes, which result from the preliminary scan, and insert the puncture needle. Since the planar images are referenced, when the puncture needle is inserted, there is often difficulty in checking a tissue located in the vicinity of the object of examination. Therefore, in the conventional X-ray CT system, it is often hard to efficiently diagnose the object of examination.